Subject: CVE-2021-47334: misc/libmasm/module: Fix two use after free in ibmasm_init_one

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

misc/libmasm/module: Fix two use after free in ibmasm_init_one

In ibmasm_init_one, it calls ibmasm_init_remote_input_dev().
Inside ibmasm_init_remote_input_dev, mouse_dev and keybd_dev are
allocated by input_allocate_device(), and assigned to
sp->remote.mouse_dev and sp->remote.keybd_dev respectively.

In the err_free_devices error branch of ibmasm_init_one,
mouse_dev and keybd_dev are freed by input_free_device(), and return
error. Then the execution runs into error_send_message error branch
of ibmasm_init_one, where ibmasm_free_remote_input_dev(sp) is called
to unregister the freed sp->remote.mouse_dev and sp->remote.keybd_dev.

My patch add a "error_init_remote" label to handle the error of
ibmasm_init_remote_input_dev(), to avoid the uaf bugs.

The Linux kernel CVE team has assigned CVE-2021-47334 to this issue.

Affected and fixed versions
===========================

	Fixed in 4.4.276 with commit 1512e7dc5eb0
	Fixed in 4.9.276 with commit 29ba8e2ba89e
	Fixed in 4.14.240 with commit 5b06ca113bf1
	Fixed in 4.19.198 with commit 481a76d4749e
	Fixed in 5.4.134 with commit 38660031e80e
	Fixed in 5.10.52 with commit b9c87ce3bc63
	Fixed in 5.12.19 with commit ef1067d2baa8
	Fixed in 5.13.4 with commit a7268e8a227d
	Fixed in 5.14 with commit 7272b591c4cb

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-47334
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	drivers/misc/ibmasm/module.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/1512e7dc5eb08b7d92a12e2bfcd9cb8c4a1ec069
	https://git.kernel.org/stable/c/29ba8e2ba89ee2862a26d91204dd5fe77ceee25a
	https://git.kernel.org/stable/c/5b06ca113bf197aab2ab61288f42506e0049fbab
	https://git.kernel.org/stable/c/481a76d4749ee3a27f902ba213fdcbb4bb39720e
	https://git.kernel.org/stable/c/38660031e80eaa6cc9370b031c180612f414b00d
	https://git.kernel.org/stable/c/b9c87ce3bc6331f82811a8cf8e930423c22523a3
	https://git.kernel.org/stable/c/ef1067d2baa847d53c9988510d99fb494de4d12c
	https://git.kernel.org/stable/c/a7268e8a227d5a4f0bd1584f556246b0224ab274
	https://git.kernel.org/stable/c/7272b591c4cb9327c43443f67b8fbae7657dd9ae